Method for harvesting fat cells from a fat-fluid mixture

ABSTRACT

The present invention teaches a method for separating a fat component of a fluid-fat mixture extracted from a patient. More particularly, the method of invention places a sponge formed of a fluid-absorbing material, such as polyvinyl acetal, in contact with the mixture so as to absorb the fluid component, thereby separating the fat component of the mixture. The separated fat component can then be injected into a selected body portion of the patient.

BACKGROUND OF THE INVENTION

The present invention relates generally to method and device for fattransplantation, and more particularly, to a sponge that can be utilizedfor autologous fat transplantation by injection of aspirated fat cells.

The advent of liposuction over two decades ago has spawned therevolutionary technique of fat transplantation by aspirating fat cellsfrom one portion of a patient body and reintroducing the fat cells to adifferent portion of the patient's body. Such lipoinjection procedureshave spread rapidly through cosmetic and reconstructive surgicalcommunities. A technique typically employed for harvesting fat forlipoinjection is tumescent local anesthesia, a process in whichsubcutaneous adipose tissue is infiltrated with large volumes of adilute local anesthesia. The adipose tissue becomes swollen and firmafter absorbing the anesthesia, allowing more accurate extraction of thefat cells by employing small diameter cannulas. Because of the infusionof anesthesia fluid into the adipose fluid, the harvested fat cells aremixed with a significant amount of anesthesia fluid when aspirated outof the patient. This fluid has to be discarded without damaging thelipocytes in order to obtain predictable and reliable results when thelipocytes are employed for lipoinjection. In fact, the quality of theresults obtained by a lipoinjection procedure is directly related to thepurity and viability of the injected fat cells. Thus, the ability toseparate the anesthesia fluid from the aspirated fat-fluid mixture iscrucial for providing fat cells of suitable quality and quantity forreintroduction into the patient.

A variety of techniques are known for separating the fluid from the fatcells. Some of these techniques include the use of a filter paper, asurgical gauze as a filter, sifters, centrifugation, and separation bygravity. All of these techniques, however, suffer from a number ofshortcomings. For example, centrifugation and separation-by-gravity canbe time consuming and inefficient.

Accordingly, there is a need for method and device that allow purifyingfat for lipoinjection in a more efficient manner.

There is also a need for such a device and method that are costeffective, and can be readily utilized by practitioners.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a method for separatingfat cells from a fat-fluid mixture extracted from a patient by employinga sponge formed of a fluid-absorbing material, such as, polyvinylacetal, to remove the fluid from the mixture. More particularly, in amethod of the invention, the sponge is brought into contact with theextracted fat-fluid mixture, for example, by placing the sponge in acontainer in which the mixture is disposed, so as to allow the sponge toabsorb the fluid component of the mixture. In this manner, the fluid isremoved from the mixture, and the remaining fat component is isolatedand can be collected. The term “fat component” as used herein refers tothe portion of the mixture that is not absorbed by the sponge, andexhibits a substantially higher fat cell density than the originalmixture. That is, the fat component may contain some fluid, albeit atmuch lower density than present in the original mixture. For example,the fat cell density of the fat component can be in a range of about 50%to 100%, and more preferably, in a range of about 80% to 100%. Thecollected fat can then be injected into a selected body portion of thepatient.

In another aspect, a sponge according to the teachings of the inventioncan include a body formed of a fluid-absorbing material, such aspolyvinyl acetal, that extends from a base to a tip. The sponge can havea variety of different shapes and sizes. For example, the sponge canhave a substantially pyramidal structure with the base and the tiphaving substantially rectangular shapes. Alternatively, the sponge canhave a substantially conical or a cylindrical structure. Further, whilein some embodiments the base has a larger area than that of the tip, inother embodiments the sponge body has a substantially uniformcross-section extending from the base to the tip.

In a related aspect, a sponge of invention has pores with sizes in arange of about 0.2 mm to about 1 mm. Further, the material forming thesponge can include a small amount of a softening agent, such as,glycerin, in order to enhance the fluid absorption properties of thesponge.

In further aspects, a sponge according to the teachings of the inventionincludes one or more channels formed therein to facilitate theabsorption of fluid by the sponge. The channels can extend from the baseto the tip, or can originate from a peripheral surface of the sponge.The channels can extend entirely or partially through the sponge body tofacilitate the uptake of the fluid from the fat-fluid mixture.

Further understanding of the invention can be obtained by reference tothe following description in conjunction with the associated drawingsdescribed briefly below.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 schematically illustrates a sponge according to the teachings ofthe invention that can be employed for harvesting fat cells from amixture of fat and fluid extracted from a patient,

FIG. 2 schematically illustrates the use of the sponge of the presentinvention for removing fluid from a fat-fluid mixture by placing thesponge of FIG. 1 in a syringe in which the fat-fluid mixture isdisposed,

FIG. 3 is another sponge according to the teachings of the inventionhaving a substantially conical body,

FIG. 4 is another sponge according to the teachings of the inventionhaving a cylindrical structure,

FIG. 5A schematically illustrates a sponge of the invention having agenerally pyramidal structure and having a plurality of channelstherein,

FIG. 5B schematically illustrates another sponge according to theteachings of the invention having a generally conical structure andhaving a plurality of channels therein, and

FIG. 6 schematically illustrates the use of a sponge according to theteachings of the invention for harvesting fat cells from a fat-fluidmixture by placing the sponge in a container in contact with a fat-fluidmixture disposed in the container.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method of separating fat cells from amixture of fat and fluid, for example, a fat-fluid mixture extractedfrom a patient, by employing a sponge, constructed in accordance withthe teachings of the invention as discussed in detail below, thatexhibits an excellent fluid-absorption property. More particularly, asdiscussed in detail below, in a method of the invention, such a spongeis brought into contact with the fat-fluid mixture so as to selectivelyabsorb the fluid component of the mixture, thereby allowing harvestingthe fat component. In the following discussion, various embodiments of asponge according to the teachings of the invention that are suitable forpracticing the separation method of the invention are presented, andfurther various steps of such a separation method are described.

FIG. 1 schematically depicts an exemplary sponge 10 according to theteachings of the invention that can be utilized for separating fat froma mixture of fat and fluid extracted from a patient, for example, from apatient's abdomen, hip or thigh. The harvested fat can then be injectedinto another body portion of the patient, e.g., the patient's face. Theexemplary sponge 10, which has a generally pyramidal structure, includesa base 12 and a tip 14 that are separated by a selected distance L. Inthis embodiment, both the base 12 and the tip 14 are formed bysubstantially rectangular surfaces having different surface areas. Inparticular, the base 12 has a surface area that is larger than that ofthe tip 14.

With continued reference to FIG. 1, the exemplary sponge 10 furtherincludes four peripheral surfaces composed of two side surfaces 16 and18, a top surface 20 and a bottom surface 22. The peripheral surfacesextend from the base 12 to the tip 14. At least one of the top surface20 and/or the opposed bottom surface 22 is slanted such that across-section of the exemplary sponge 10 on any plane parallel to thebase and tip surfaces exhibits a rectangular shape whose area increasescontinuously from the tip to the base.

The exemplary sponge 10 further includes a plurality of threads 24coupled to the tip 12 that can be utilized for removing the sponge froma container in which fat-fluid mixture is disposed subsequent to theabsorption of the fluid component by the sponge, as described below.

The sponge 10 can have any desired size that is suitable for aparticular embodiment of a separation method of the invention. Forexample, the sponge 10 can be shaped and sized so as to fit within aconventional surgical syringe in which the fat-fluid mixture isdisposed. Alternatively, the sponge 10 can be sized to efficientlyabsorb the fluid component of a fat-fluid mixture disposed in anothercontainer. By way of example only, the lengths A and B of the two sidesof the rectangular base 12 can be selected to be in a range of about afew millimeters to about tens of centimeters, e.g., A can be 15 mm whileB is 6 mm. A similar range can be selected for the lengths E and D ofthe two sides of the tip 14, e.g, E can be 6 mm while D is 6 nm. Thelength L of the sponge can also be selected within a wide range ofvalues, e.g., from a few millimeter to tens of centimeter, such as 150mm.

The sponge 10 can be constructed by utilizing a variety of manufacturingtechniques known in the art. In some preferred embodiments of theinvention, the sponge 10 is formed of polyvinyl acetal by cross linkingpolyvinyl alcohol while simultaneously adding air. In some embodiments,a small amount, e.g., less than about 1 percent, of glycerin is added asa softening and wetting agent in order to enhance the fluid absorptionproperties of the sponge. The sponge 10 can have pores with sizes in arange of about 0.2 mm to about 1 mm. Further, the threads 24 can beformed of nylon. Those having ordinary skill in the art will appreciatethat other materials can also be employed for forming the sponge 10 solong as the material exhibits fluid-absorption properties needed forproper functioning of the sponge for separating fat from a fluid-fatmixture.

With reference to FIG. 2, in one embodiment of a separation method ofthe invention, the sponge 10 can be utilized for harvesting fat cellsfrom a mixture of fat and fluid removed from a patient, and moreparticularly, for small volume fat transfers, as described below. Forexample, the sponge can be placed, with its base first, into a syringe26 subsequent to removing the syringe's plunger. A mixture of fat andfluid (not shown), which has been removed from a patient, can then beplaced into the syringe over the sponge. The sponge quickly andefficiently absorbs the fluid, leaving behind purified viable fat thatcan be utilized for injection into the patient. The sponge can be keptin contact with the mixture for a sufficient duration to allow it toabsorb a substantial amount of the fluid component, and preferably theentire fluid component. For example, the sponge can be kept in contactwith the fluid for a sufficient duration so as to result in saturationof the sponge with the fluid component. In some cases, the remaining fatcomponent may still contain a volume of the fluid. Such a fat componentcan be further purified by application of an additional sponge of theinvention, as discussed below.

The sponge can then be removed from the syringe and the purified fat canbe transferred from the syringe to smaller syringes for injection. Thevolume of fat obtained after purification by the sponge 10 is typicallyone-third of the volume of fat and fluid originally applied to thesyringe in which the sponge is placed. Those having ordinary skill inthe art will appreciate that other results can be obtained depending,for example, on the shape and size of a sponge that is utilized and/orduration of the contact of the sponge with the mixture.

Different syringe and sponge sizes can be utilized. Further, the fat canbe separated from the fat-fluid mixture by repeated application of asponge of the invention, such as the above sponge 10, to the samemixture. That is, subsequent to an initial application of the sponge tothe mixture, and removal of a selected amount of the fluid, anothersponge can be applied to the partially purified sample to removeadditional fluid, thereby enhancing the purity of the harvested fat.This process can be repeated as many times as needed to obtain a desiredpurity of the harvested fat.

A separation method of the invention provides distinct advantages overconventional fat purification techniques. For example, to evaluateefficacy of a method of the invention for fat purification in comparisonwith the separation-by-gravity technique, fat was passively separatedfrom a mixture of fat and fluid over a four-day period by employingseparation-by-gravity. A sponge of the invention was then placed in thegravity-purified fat. The sponge absorbed enough fluid from thegravity-purified fat to reduce its volume by approximately 25%. That is,the sponge substantially improved the purification of the fat that washarvested by utilizing the separation-by-gravity technique. Moreover,the fat cells purified by the sponge of the invention were examined andfound to be completely normal and unaffected by the purificationprocess. Thus, the separation method of the invention is superior topassive separation techniques.

Further, a sponge of the invention, for example, the exemplary sponge10, is simple to use, highly effective for fat purification, and can beprovided in a sterile, prepackaged form for easy storage in an office ora surgical facility.

Fat obtained through a method of the invention can be employed to obtainthe most concentrated and viable fat grafts to date, thereby enhancingpredictability and success of cosmetic and surgical procedures. Forexample, areas that are conventionally classified as poor recipientsites can become viable candidates for lipoinjection by utilizing fatharvested by employing the method of the invention. Hence, the method ofthe invention can significantly lower the incidence of graft loss orpartial take, thus obviating the need to overtreat. This is especiallyadvantageous when treating a patient's face.

It should be understood that the structure of a sponge according to theteachings of the invention is not limited to that described above. Infact, a sponge of the invention can be made of a fluid-absorbingmaterial, such as polyvinyl acetal, in a variety of shapes and sizes toharvest fat cells from a mixture of fat and fluid. For example, FIG. 3schematically illustrates another sponge 28 according to the teachingsof the invention that is formed of a generally conical body that extendsfrom a substantially circular base 30 to a substantially circular tip32. Similar to the previous sponge 10, the base 30 of this sponge has alarger cross-sectional area than that of the tip 32. Further, one ormore threads 24, e.g., nylon threads, can be optionally attached to thetip 32 to facilitate removal of the sponge from a container, e.g., asyringe.

By way of another example, FIG. 4 schematically illustrates anothersponge 34 according to the teachings of the invention that includes asubstantially cylindrical body that extends from a circular base 36 to acircular tip 38. Unlike the above embodiments, the sponge 34 exhibits asubstantially uniform cross-section extending from the base 36 to thetip 38. The cross-sectional area of the sponge 34 in a planeperpendicular to a longitudinal axis extending from the base to the tip,and its length can have a variety of sizes selected, for example, basedon the size of the container in which the sponge is placed forharvesting fat. For example, the cross-sectional area of the sponge 34can be in a range of about 5 mm² to about 100 cm² while the length ofthe sponge 34 can take values in a range from about 5 mm to about 50 cm.Those having ordinary skill in the art will appreciate that other sizescan also be utilized.

In other aspects, a sponge of the invention can include one or morechannels therein for facilitating absorption of fluid by the sponge. Forexample, FIG. 5A illustrates a sponge 40 of the invention that exhibitsa generally pyramidal structure and further includes two channels 42 and44 that extend from its base 46 to its tip 48, and a channel 50 thatoriginates at its base and partially penetrates the sponge body. Thosehaving ordinary skill in the art will appreciate that one or morechannels that originate from any of the peripheral surfaces of thesponge and extend either to the base or the tip, or one of the otherperipheral surfaces, or extend partially into the sponge body can alsobe provided.

By way of another example, FIGURE SB schematically illustrates anothersponge 52 of the invention having a generally conical body in which aplurality of channels 54 a, 54 b, 54 c, and 54 d, herein collectivelyreferred to as channels 54, are formed. While the channel 54 a spans theentire cross-section of the sponge 52, the channels 54 b, 54 c, and 54 dextend only partially through the sponge body.

As discussed above, a sponge of the invention can be employed to removefluid from a mixture of fat and fluid extracted from a patient byutilizing, for example, a tumescent local anesthesia technique. Forexample, according to one embodiment described above, a sponge of theinvention can be inserted into a syringe in which a fat-fluid mixture isdisposed in order to remove fluid from the fat. It should, however, beunderstood that a method of the invention can be practiced by placing afat-fluid mixture in any desired container, e.g., syringes of differentsizes or a dish, and utilizing a sponge of the invention that is sizedand shaped in order to fit in the container to remove a volume of thefluid from the mixture. By way of example, FIG. 6 illustrates acontainer 56 in which a cylindrical sponge 58 of the invention canplaced to absorb fluid from a fat-fluid mixture extracted from a patientand disposed in the container.

In another aspect, the invention provides a medical kit for separatingfat from a fat-fluid mixture extracted from a patient. Such a medicalkit can include a sterile sponge according to the teachings of theinvention, such as those described above, that is formed of afluid-absorbing material, e.g., polyvinyl acetal, and a sterilecontainer, e.g., a syringe from which the plunger is removed, in which afat-fluid mixture extracted from a patient can be disposed. Further, themedical kit can include a sterile device, e.g., a syringe, that can beemployed to collect the separated fat component.

Those having ordinary skill in the art will appreciate that variousmodifications can be made to the above embodiments without departingfrom the scope of the present invention. For example, the method of theinvention can be practiced by employing a sponge made in various sizesand shapes in accordance with the teachings of the invention.

1-8. (canceled)
 9. A medical sponge, comprising a body formed of afluid-absorbing material extending from a base to a tip and beingeffective for absorbing fluid from a mixture of fat and fluid extractedfrom a patient.
 10. The medical sponge of claim 9, wherein said base hasan area larger than a corresponding area of said tip.
 11. The medicalsponge of claim 9, wherein said body has a substantially pyramidalstructure and said base and said tip are substantially rectangularsurfaces.
 12. The medical sponge of claim 9, wherein said body has asubstantially conical structure and said base and said tip aresubstantially circular surfaces.
 13. The medical sponge of claim 9,wherein said body has a substantially cylindrical structure.
 14. Amedical sponge, comprising a body formed of a fluid-absorbing materialand extending from a base to a tip, said base having a largercross-sectional area than said tip, wherein said sponge is effective forfiltering fat from a mixture of fat and fluid extracted from a patient.15. The medical sponge of claim 14, wherein said sponge is formed ofpolyvinyl acetal.
 16. The medical sponge of claim 14, wherein said baseand said tip are formed as substantially rectangular surfaces.
 17. Themedical sponge of claim 14, wherein said body further comprises fourperipheral surfaces each extending from said base to said tip.
 18. Themedical sponge of claim 16, wherein said base and said tip surfaces aresubstantially parallel.
 19. The medical sponge of claim 16, wherein saidbody exhibits a substantially rectangular cross-section at any planeparallel to said base and tip surfaces such that an area of saidsubstantially rectangular cross-section increases continuously from saidtip to said base.
 20. The medical sponge of claim 14, wherein any ofsaid base or said tip has an area in a range of about a few mm2 to a fewcm2.
 21. The medical sponge of claim 14, wherein said base is separatedfrom said tip by a distance in a range of about a few millimeters toabout a few centimeters.
 22. The medical sponge of claim 14, furthercomprising one or more channels extending from said base to said tip tofacilitate the separation of fluid from a fat-fluid mixture.
 23. Themedical sponge of claim 14, further comprising one or more channelshaving an end positioned at any of said base or said tip and extendingat least partially through said body.
 24. The medical sponge of claim17, further comprising one or more channels having an end positioned atany of said peripheral surfaces and extending at least partially throughsaid body.
 25. A medical kit for separating fat component of a fat-fluidmixture, comprising a sterile container for storing the fat-fluidmixture, a sterile sponge formed of a fluid-absorbing material and sizedand shaped so as to fit in said container in at least partial contactwith said stored mixture thereby absorbing the fluid component of themixture to separate the fat component, and a sterile device configuredfor collecting the separated fat component.